Gaseous electric discharge device



May 26, 1936.

H. KREFFT GASEOUS ELECTRIC DISCHARGE DEVI GE Filed Nov. 5, 1932 n l! H II INVENTOR ATTORNEY Patented May 26, 1936 UNITED STATES I 2,042,261 GASEOUS ELECTRIC DISCHARGE DEVICE Hermann Krefft, Berlin-Schmargendori', Germany, assignor to General Electric Company, a corporation of New York Application November 3, 1932, Serial No. 641,053 In Germany November 6, 1931 3 Claims.

The present invention relates to gaseous electric discharge devices generally and more particularly the invention relates to such devices emittin light the spectrum of whch is a close approximation of the spectrum of daylight.

Heretofore high intensity, gas filled incandescent lamps provided with a flue filter, or an electric discharge device having a filling of carbon dioxide gas have been used, as light sources having a spectrum closest to that of daylight, the light from the latter being a better approximation of daylight than that of the former. As is well known, carbon dioxide lamps are inefilcient and require a gas feeding means as the carbon dioxide does not last very long.

The object of the present invention is to provide a gaseous electric discharge lamp device the emitted light of which closely approaches daylight. Another object of the invention is to provide such a device of simple structure. Still further objects and advantages attaching to the device and to its use and operation will be apparent to those skilled in the art from the following particular description and from the appended claims.

The invention comprises an electric discharge device filled with a mixture of a rare gas and caesium vapor and/ or rubidium vapor and means to maintain the container of the device at a temperature of 150 C. The pressure of the caesium or rubidium is 0.02 mm. or more at such temperature of the container. At the normal temperature of the container which is, for example, approximately 100 C. the vapor pressure of the alkali metal vapor is less than 0.001 mm. At this pressure the spectrum of the caesium and rubidium vapor is strong in blue and red-violet respectively. When the vapor pressure of these alkali metal vapors is greater than 0.001, as in the device of the present invention, and a particular rare gas is used the spectral lines of said vapor whichare weak at a pressure of 0.001 are strengthened and the spectrum of the gas filling fills in or complements the lines missing in the vapor spectrum so that the spectrum of the light emitted by an electric discharge device made in accordance with the present invention is proportionate over all wavelengths and the spectrum of said light is a close approximation of that of daylight or white light.

Prior daylight lamps using caesium or rubidium vapor as a component of the gaseous filling have required a. gas feeding means to replenish the rare gasprincipal filling as said gas quickly disappeared due to the trapping of the gas against the container walls by the sputtered electrode particles or from other causes. This is avoided in the device of the present invention by the use of non-sputtering, sintered, mixed metal and oxide electrodes which will be more fully disclosed later herein. An advantageous feature of the device made in accordance with the present invention is that it has a strong emission of infrared rays in the region between 3.6 mu and 0.8 mu which enhances sunlight effect of the device.

The container of the device is maintained at temperature higher than normal by using thermionicelectrodes, which permit the use of high current density, and by covering the electrode chambers with heat insulating material. As caesium and rubidium vapor have approximately the same pressures at like temperatures a mixture including both of said vapors and a rare gas is used when desired.

In the drawing accompanyi and forming part of this specification an embodiment of my invention is shown in a side elevational, partly sectional view, but as such illustration is primarily for purposes of disclosure it will be understood of course that numerous changes in.the form and details of the device and in its use and operation may be made by those skilled in the art without departure from the broad spirit and scope of the invention.

Referring to the drawing the new and novel gaseous electric discharge device comprises a container I. A thermionic electrode comprising a rod of electron emitting material, such as barium oxide, or a rod of sintered, mixed metal and electron emitting material such as tungsten and barium oxide, surrounded and supported by a heating filament 3, such as a. tungsten filament, is located at each end of said container I. Each of said electrodes 2, 3 is supported by current inleads 4 and 5 sealed into the stem 6 of said container l Said container I is filled with a mixture of a rare gas, such as argon or neon at 1 mm. pressure and an alkali metal vapor, such as caesium vapor, or rubidium vapor, or mixtures of 'both where desired. The parts of said container I adjacent said electrodes 2, 3 are covered with a heat insulation material, such as an asbestos jacket 8, to prevent condensation of the metal vapor at said parts which are the coolest portions of the container during the operation of the device. The rubidium or caesium is maintained in a vaporized condition in the discharge path in the device by the heat of the discharge.

The device is started into operation by connecting said leads 4 and 5 to a suitable source of current which heats said electrodes 2, 3 to anelectron emitting temperature. When said electrodes have attained their operating temperature the operating potential is applied to one of the electrode leads 4 or 5 and the gaseous electric discharge starts in the device. When the discharge first starts the rare gas conducts the dis charge between said electrodes 2, 3 until the vaporizable material, indicated at I, is vaporized by the heat of the discharge in said gaseous atmosphere. when said vaporizable material is completely vaporized the light emitted from the device is that of the gas and vapor mixture and as pointed out above the spectrum of this light closely approaches that of daylight or white light.

It will of course be understood that said container l is made of a glass resistant to the chemical action of the caesium and rubidium vapor 4-5 N320 11-13 A1203 10-11 C80 40-60 B203 10-25 $102 Containers made of a glass having the above composition are chemically stable in the presence oi. alkali metal vapors, such as caesium and rubidium vapor, and do not melt under a temperature of 500 C. or higher.

What I claim as new and desire to secure by Letters Patent of the United States is:-

1. An electric discharge device comprising a container, thermionic electrodes sealed therein, a gaseous atmosphere therein, said gaseous atmosphere comprising a mixture of rare gas, caesium and rubidium vapor.

2. An electric discharge device comprising a container, thermionic electrodes sealed therein, a gaseous atmosphere therein, said gaseous atmosphere comprising a mixture of argon, caesium and rubidium vapor.

3. An electric discharge device comprising a container, thermionic electrodes sealed therein, a gaseous atmosphere therein, said gaseous atmosphere comprising a mixture of neon, caesium and rubidium vapor.

HERMANN KREFFT. 

